#include "sofa.h"

void iauFw2m(double gamb, double phib, double psi, double eps,
             double r[3][3])
/*
**  - - - - - - - -
**   i a u F w 2 m
**  - - - - - - - -
**
**  Form rotation matrix given the Fukushima-Williams angles.
**
**  This function is part of the International Astronomical Union's
**  SOFA (Standards Of Fundamental Astronomy) software collection.
**
**  Status:  support function.
**
**  Given:
**     gamb     double         F-W angle gamma_bar (radians)
**     phib     double         F-W angle phi_bar (radians)
**     psi      double         F-W angle psi (radians)
**     eps      double         F-W angle epsilon (radians)
**
**  Returned:
**     r        double[3][3]   rotation matrix
**
**  Notes:
**
**  1) Naming the following points:
**
**           e = J2000.0 ecliptic pole,
**           p = GCRS pole,
**           E = ecliptic pole of date,
**     and   P = CIP,
**
**     the four Fukushima-Williams angles are as follows:
**
**        gamb = gamma = epE
**        phib = phi = pE
**        psi = psi = pEP
**        eps = epsilon = EP
**
**  2) The matrix representing the combined effects of frame bias,
**     precession and nutation is:
**
**        NxPxB = R_1(-eps).R_3(-psi).R_1(phib).R_3(gamb)
**
**  3) The present function can construct three different matrices,
**     depending on which angles are supplied as the arguments gamb,
**     phib, psi and eps:
**
**     o  To obtain the nutation x precession x frame bias matrix,
**        first generate the four precession angles known conventionally
**        as gamma_bar, phi_bar, psi_bar and epsilon_A, then generate
**        the nutation components Dpsi and Depsilon and add them to
**        psi_bar and epsilon_A, and finally call the present function
**        using those four angles as arguments.
**
**     o  To obtain the precession x frame bias matrix, generate the
**        four precession angles and call the present function.
**
**     o  To obtain the frame bias matrix, generate the four precession
**        angles for date J2000.0 and call the present function.
**
**     The nutation-only and precession-only matrices can if necessary
**     be obtained by combining these three appropriately.
**
**  Called:
**     iauIr        initialize r-matrix to identity
**     iauRz        rotate around Z-axis
**     iauRx        rotate around X-axis
**
**  References:
**
**     Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
**
**     Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
**
**  This revision:  2021 May 11
**
**  SOFA release 2021-05-12
**
**  Copyright (C) 2021 IAU SOFA Board.  See notes at end.
*/
{
/* Construct the matrix. */
   iauIr(r);
   iauRz(gamb, r);
   iauRx(phib, r);
   iauRz(-psi, r);
   iauRx(-eps, r);

/* Finished. */

/*----------------------------------------------------------------------
**
**  Copyright (C) 2021
**  Standards Of Fundamental Astronomy Board
**  of the International Astronomical Union.
**
**  =====================
**  SOFA Software License
**  =====================
**
**  NOTICE TO USER:
**
**  BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
**  CONDITIONS WHICH APPLY TO ITS USE.
**
**  1. The Software is owned by the IAU SOFA Board ("SOFA").
**
**  2. Permission is granted to anyone to use the SOFA software for any
**     purpose, including commercial applications, free of charge and
**     without payment of royalties, subject to the conditions and
**     restrictions listed below.
**
**  3. You (the user) may copy and distribute SOFA source code to others,
**     and use and adapt its code and algorithms in your own software,
**     on a world-wide, royalty-free basis.  That portion of your
**     distribution that does not consist of intact and unchanged copies
**     of SOFA source code files is a "derived work" that must comply
**     with the following requirements:
**
**     a) Your work shall be marked or carry a statement that it
**        (i) uses routines and computations derived by you from
**        software provided by SOFA under license to you; and
**        (ii) does not itself constitute software provided by and/or
**        endorsed by SOFA.
**
**     b) The source code of your derived work must contain descriptions
**        of how the derived work is based upon, contains and/or differs
**        from the original SOFA software.
**
**     c) The names of all routines in your derived work shall not
**        include the prefix "iau" or "sofa" or trivial modifications
**        thereof such as changes of case.
**
**     d) The origin of the SOFA components of your derived work must
**        not be misrepresented;  you must not claim that you wrote the
**        original software, nor file a patent application for SOFA
**        software or algorithms embedded in the SOFA software.
**
**     e) These requirements must be reproduced intact in any source
**        distribution and shall apply to anyone to whom you have
**        granted a further right to modify the source code of your
**        derived work.
**
**     Note that, as originally distributed, the SOFA software is
**     intended to be a definitive implementation of the IAU standards,
**     and consequently third-party modifications are discouraged.  All
**     variations, no matter how minor, must be explicitly marked as
**     such, as explained above.
**
**  4. You shall not cause the SOFA software to be brought into
**     disrepute, either by misuse, or use for inappropriate tasks, or
**     by inappropriate modification.
**
**  5. The SOFA software is provided "as is" and SOFA makes no warranty
**     as to its use or performance.   SOFA does not and cannot warrant
**     the performance or results which the user may obtain by using the
**     SOFA software.  SOFA makes no warranties, express or implied, as
**     to non-infringement of third party rights, merchantability, or
**     fitness for any particular purpose.  In no event will SOFA be
**     liable to the user for any consequential, incidental, or special
**     damages, including any lost profits or lost savings, even if a
**     SOFA representative has been advised of such damages, or for any
**     claim by any third party.
**
**  6. The provision of any version of the SOFA software under the terms
**     and conditions specified herein does not imply that future
**     versions will also be made available under the same terms and
**     conditions.
*
**  In any published work or commercial product which uses the SOFA
**  software directly, acknowledgement (see www.iausofa.org) is
**  appreciated.
**
**  Correspondence concerning SOFA software should be addressed as
**  follows:
**
**      By email:  sofa@ukho.gov.uk
**      By post:   IAU SOFA Center
**                 HM Nautical Almanac Office
**                 UK Hydrographic Office
**                 Admiralty Way, Taunton
**                 Somerset, TA1 2DN
**                 United Kingdom
**
**--------------------------------------------------------------------*/
}
